Not sure about it in delphi, can think of 4 or 5 ways in other stuff..
Its basically just an acl right but not that advanced, couldnt you set it to use the users local time and just have two options in the applet that are:
Restricted Time: 09:30P Restore Full Bandwidth: 06:00A
Obviously it isnt that easy but best way would have it pull from the users (or in thiscase servers) local time, using the same code you use to restrict it. (Download limit X, or Download limit <blank>)
What do others think?
-Kurt